An airplane is propelled by one or more propulsion assemblies comprising a turbojet engine housed in a tubular nacelle. Each propulsion assembly is attached to the airplane by a pylon situated generally under a wing or at the fuselage.
A nacelle generally has a structure comprising an air intake upstream of the engine, a central section intended to surround a fan of the turbojet engine, a downstream section housing thrust reverser means and intended to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream of the turbojet engine.
The air intake comprises, on one hand, an air intake lip adapted to allow optimal collection towards the turbojet engine of the air necessary to supply the fan and the internal compressors of the turbojet engine, and on the other hand, a downstream structure on which the lip is attached and intended to channel the air suitably towards the vanes of the fan. The assembly is attached upstream of a case of the fan belonging to the central section of the nacelle.
Depending on the temperature and relative humidity conditions on the ground or in flight, ice may form on the profile of the lip, in particular at the inner profile. This ice formation can be dangerous for the mechanical operation of the stationary and rotating parts of the engine and can cause a decrease in performance. Deicing systems for this part of the air intake lip have therefore been developed to resolve this problem. Examples in particular include documents U.S. Pat. No. 4,688,757 and EP 1 495 963, as well as the application registered under number FR 06/02547.
Currently, maintenance operations on this equipment housed inside the air intake structure require the builders to provide access hatches to the various pieces of equipment. Despite the efforts made to optimize the positioning of the hatches and allow the easiest possible access, it is sometimes necessary to reach the internal equipment of the air intake structure using specific tools, such as an endoscope, which is not fully satisfactory in terms of monitoring this equipment.
Moreover, in the event it is necessary to replace part of the internal equipment, it will be necessary to take out the entire air intake structure, which requires significant tools and causes immobilization of the propulsion assembly and therefore of the airplane in general.
It will also be noted that the conditions for exploitation and maintenance of an air intake require distinct components, such as a sectorized modular lip as well as an easily removable outer panel due to their high replacement rate as a result of their direct exposure to the outside environment and any projectiles. These constraints significantly reduce the integrity of the general aerodynamic line of the air intake structure, which the presence of access hatches further aggravates.
Solutions have been presented in document U.S. Pat. No. 5,609,313 and application FR 06/08599. In order to offset the mentioned drawbacks, these documents provide a turbojet engine nacelle comprising an air intake structure that can be translated forward and thereby at least partially exposing the inside of the nacelle.
Thus, by incorporating the air intake lip into the outer panel so as to form a single disassemblable piece, disassembly and partial replacement of the air intake structure are possible and made easier. Furthermore, the disassembly thus facilitated also makes it possible to open the air intake structure to access internal equipment without demanding substantial and complicated maneuvers or requiring a long immobilization time.
These mobile cowls are generally mounted on a rail/slide system comprising a plurality of rails arranged around the nacelle. Application FR 07/09105 proposes an installation of these rails on the fan case.
However, the number of guide means used makes the nacelle heavier and there is therefore a need to improve such a mobile cowl system requiring fewer guide rails while preserving good integrity of the structure.
Furthermore, the guide structures described in these documents are generally less suited to nacelles arranged at the fuselage of an aircraft and for which the attachment pylon is substantially horizontal.